.450 Bushmaster Complete Assembled Upper – Right Handed

Description As of March 2026, lead time for a complete upper to be shipped, is 5-10 days. Complete ready to fire upper, with your choice of a 10.5″, 12.5″, 16″ or 18″ lightweight barrel. Base model includes a 6061 M4 style upper receiver, barrel of your choice, black A1 style flash hider, black gas block, complete bolt/carrier group, and charging handle.  You must select a hand guard option or have no hand guard installed in order to purchase this item. Barrels are available in 12.5″, 16.25″, and 18″ dimpled for gas block screw alignment.  An adjustable gas block is recommended for Suppressed use. Light-Weight barrel profile is 790″ under the hand guards, .750″ at the gas block, and .730″ at the muzzle. 12.5″ Barrels have a carbine length gas system, 5/8-24 muzzle thread, 4150 steel, 1:20 twist.  1.20 pounds.  Requires adjustable gas block for Super Sonic and Suppressed use. 16″ Barrels have a carbine length gas system, 5/8-24 muzzle thread, 4150 steel, 1:24 twist.  1.52 pounds. 18″ Barrels have a mid-length gas system, 5/8-24 muzzle thread, 4150 steel, 1:24 twist.  1.70 pounds Upgrade your upper with the Midwest Industries CRM M-Lok hand guard. Also available with upgraded heavy duty Tromix 7075 billet receiver, various muzzle attachments, engraved ejection port cover, etc. Black chromoly barrels are externally coated with 2400 Series Bake-On GunKote. With a Tromix 16″ light weight barrel, optional Midwest-Industries 9.25″ CRM M-Lok hand guard, and optional thread protector, the complete rifle weight on a standard M4 style lower is 5.49 pounds. Pics shown with optional Midwest Industries CRM M-Lok hand guard installed. All Tromix uppers are test fired prior to shipping. SB 704 applies to all California sales – Must ship to FFL.